Class: FFI::StructLayoutBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/ffi/struct_layout_builder.rb

Constant Summary

NUMBER_TYPES = 
[
  Type::INT8,
  Type::UINT8,
  Type::INT16,
  Type::UINT16,
  Type::INT32,
  Type::UINT32,
  Type::LONG,
  Type::ULONG,
  Type::INT64,
  Type::UINT64,
  Type::FLOAT32,
  Type::FLOAT64,
  Type::LONGDOUBLE,
  Type::BOOL,
]

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (StructLayoutBuilder) initialize

A new instance of StructLayoutBuilder



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# File 'lib/ffi/struct_layout_builder.rb', line 25

def initialize
  @size = 0
  @alignment = 1
  @min_alignment = 1
  @packed = false
  @union = false
  @fields = Array.new
end

Instance Attribute Details

- (Object) alignment

Returns the value of attribute alignment



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# File 'lib/ffi/struct_layout_builder.rb', line 23

def alignment
  @alignment
end

- (Object) size

Returns the value of attribute size



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# File 'lib/ffi/struct_layout_builder.rb', line 23

def size
  @size
end

Instance Method Details

- (Object) add(name, type, offset = nil) 



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# File 'lib/ffi/struct_layout_builder.rb', line 78

def add(name, type, offset = nil)

  if offset.nil? || offset == -1
    offset = @union ? 0 : align(@size, @packed ? [ @packed, type.alignment ].min : [ @min_alignment, type.alignment ].max)
  end

  #
  # If a FFI::Type type was passed in as the field arg, try and convert to a StructLayout::Field instance
  #
  field = type.is_a?(StructLayout::Field) ? type : field_for_type(name, offset, type)
  @fields << field
  @alignment = [ @alignment, field.alignment ].max unless @packed
  @size = [ @size, field.size + (@union ? 0 : field.offset) ].max

  return self
end

- (Object) add_array(name, type, count, offset = nil) 



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# File 'lib/ffi/struct_layout_builder.rb', line 103

def add_array(name, type, count, offset = nil)
  add(name, Type::Array.new(type, count), offset)
end

- (Object) add_field(name, type, offset = nil) 



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# File 'lib/ffi/struct_layout_builder.rb', line 95

def add_field(name, type, offset = nil)
  add(name, type, offset)
end

- (Object) add_struct(name, type, offset = nil) 



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# File 'lib/ffi/struct_layout_builder.rb', line 99

def add_struct(name, type, offset = nil)
  add(name, Type::Struct.new(type), offset)
end

- (Object) align(offset, align) (private) 



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# File 'lib/ffi/struct_layout_builder.rb', line 118

def align(offset, align)
  align + ((offset - 1) & ~(align - 1));
end

- (Object) build 



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# File 'lib/ffi/struct_layout_builder.rb', line 107

def build
  # Add tail padding if the struct is not packed
  size = @packed ? @size : align(@size, @alignment)
  
  layout = StructLayout.new(@fields, size, @alignment)
  layout.__union! if @union
  layout
end

- (Object) field_for_type(name, offset, type) (private) 



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# File 'lib/ffi/struct_layout_builder.rb', line 122

def field_for_type(name, offset, type)
  field_class = case
  when type.is_a?(Type::Function)
    StructLayout::Function

  when type.is_a?(Type::Struct)
    StructLayout::InnerStruct

  when type.is_a?(Type::Array)
    StructLayout::Array

  when type.is_a?(FFI::Enum)
    StructLayout::Enum

  when NUMBER_TYPES.include?(type)
    StructLayout::Number

  when type == Type::POINTER
    StructLayout::Pointer

  when type == Type::STRING
    StructLayout::String

  when type.is_a?(Class) && type < StructLayout::Field
    type

  when type.is_a?(DataConverter)
    return StructLayout::Mapped.new(name, offset, Type::Mapped.new(type), field_for_type(name, offset, type.native_type))

  when type.is_a?(Type::Mapped)
    return StructLayout::Mapped.new(name, offset, type, field_for_type(name, offset, type.native_type))

  else
    raise TypeError, "invalid struct field type #{type.inspect}"
  end

  field_class.new(name, offset, type)
end

- (Object) packed=(packed) 



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# File 'lib/ffi/struct_layout_builder.rb', line 51

def packed=(packed)
  if packed.is_a?(Fixnum)
    @alignment = packed
    @packed = packed
  else
    @packed = packed ? 1 : 0
  end
end

- (Object) union=(is_union) 



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# File 'lib/ffi/struct_layout_builder.rb', line 43

def union=(is_union)
  @union = is_union
end

- (Boolean) union?

Returns:

  • (Boolean) 


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# File 'lib/ffi/struct_layout_builder.rb', line 47

def union?
  @union
end